Apparatus for recordation and reproduction of sound



Feb, 16, 1932.. w. RICHMOND 1,845,988

APPARATUS FOR REGORDATION AND REPRODUCTION OF SOUND Original Filed March'12. 1920 2 Sheets-Sheet 1 Jwwmtoz Feb. 16, 1932. w. RICHMOND 1,845,988

APPARATUS FOR REdORDATION AND REPRODUCTION OF SOUND Original Filed March12. 1920 2 Sheets-Sheet 2 w lb , m M M I 17 315 Patented Feh. 16, 1932ino; STATES WALTER RICHMOND, 0F CLEVELAND, OHIQ AlEPTUh 380R RECORDATION.ANJD REPRODUCTION OF SOUND tlrtygtnal application tiled March 12, 1920,serial No; 365,320. Divided and this application filed December o, 1930.Serial No. 500,661. i

This invention relates to a method and apparatus for translating soundand is in the nature of a divisional application of my e c-pendingapplication Serial No. 365,320, led March 12, 1920, on an apparatus fortranslating sound.

This invention relates to a method of and apparatus for translatinsound. Heretofore the translation ot sound Waves'considerablediihculties have been. experienced in recording and reproducing soundwaves clearly.

These various dii'ficulties, their causes and ettects, and the manner inwhich I have over- L "is them and made possible true and clearrecordation and reproduction of sound of controlled volume will becomeapparent from the following specification.

One object of my invention is to eliminate desirable vibrations ofvarious parts of the recording or reproducing apparatus, to record andreproduce the original sound es and to reduce distortion or in otherwaves.

i nether object of my invention is to rcproduce the original sound wavesand at the 0 me time eliminate all other sound Waves ch from variouscauses inherent in pres entreproducers fund their way into theamplifying devices of commercial translating devices and mingle with theoriginal sound waves to an objectionable extent.

Another object of my invention is to transone class of waves intoequivalent waves of another class and to retranslate from this classinto the original class of wave in smallner such that the final wavesuitors no serious deterioration from its several translations, 4% iuother object of my invention is the substa tial translation oat soundwaves into their equivalent mechanical or electrical waves or thereverse, the translation of mechanical or electrical waves substantiallyinto their equivalent sound Waves without a. noticeable addition orintroduction of interfering waves.

Another object of my invention is to produce a diaphragm so delicatelypoised that it will respond to very slight variation in tone ormagnitude of vibration and which is at the same time so constructed andactuatedv that it can swing through a greater amplitude than thegreatest amplitude of vibratlon to which it will be subjected in use,thus enabling the reproduction of sound waves of reater volume than theoriginal waves l'ree rom noticeable distortion in tone or clearness.

Another object oi my invention is a diaphragm which will not lagappreciably hehind the impressed vibration but will reach the limit ofits greatest vibration substantially in unison with the impressedvibration and which will return to its normal position as rapidly as thecycle of the particular'tfine which is being impressed.

Another ob ect of my invention is a diaphragm, different portions ofwhich have different periods o-t vibration or diflerent key notes,

Another object of my invention is a diaphragm which, as a whole, has nokey note.

Another object of my invention is to ob- -tain clear enunciation in thetranslation oft sound Waves.

Another object of my invention is to im prove the reproduction of thehuman voice and other tones and to reduce 'the harsh, metallic,mechanical sounds such as are produced by many commonly used translatingdevices.

Another object of my invention is to record and reproduce sound waves sothat they have substantially the same volume as the original sound Waveswithout seriouslyirnpairing the quality of tone or enunciation asdistinguished tronrvarious expediencies which have been in use, such. asthe fibre needle which pro duces fairly good tones but of such low vol-'ume as to he undesirable.

(lther novel features of my invention are described and claimed inthe'co-pending ap-' plication above referred to and in m coipendingapplication, Sen No, 500,660, filed of Fig. 2.

Fig. 5 is a reduced view of the left half of the reproducer asillustrated in Fig. 1, and is taken on a plane indicated by the line BBof Fig. 1.

Fig. 6 is a side elevation of the body member of the reproducerillustrated in Figs. 1 and 2 illustrating the mounting of the stylusbar. thereon and the rubber spacing ring and diaphragm.

Fig. 7 is a detail plan view of one form of torsion spring suitable foruse in my invention.

Fig. 8 is a side elevation of the clamping ringof the reproducerillustrated showing another means for mounting the torsion spring.

Fig. 9 is a plan view of a diaphragm suitable for use in my reproducer.

Figs. 10, 11 and 12 are cross sectional views illustrating forms ofdiaphragms which may be used in connection with my invention.

Fig. 13 is a cross-sectional view of a diaphragm similar tothat'illustrated in Fig. 9, and is taken on a plane through the centerthereof. Fig. 14 is a cross-sectional-view of a preferred form of throatfor use in my reproducer and is taken on a plane indicated by the lineAA of Fig. 5.

Referring to the drawings, Fig. 1 illustrates one embodiment of myinvention in a reproducer having a body member 1 or principal part towhich other parts are attached. This body portion may be of eithermetal'or" wood and is preferably in the form of a disk having a centralopening in which is mounted the sound tube 2 for the transmission ofsound waves to any amplifying device to which the reproducer may beattached. As

illustrated in Figs. 1 and 2, a diaphragm 3 is mounted on the body 1 bya clamping ring 4, the diaphragm being spaced from the body 1 by arubber ring 5. This assemblagemay be conveniently made by clamping thering .4 against the body 1 by means of screws such as 6 and 7. In theform illustrated, the sound tube 2 passes through the body 1 andterminates in the plane of the face of the body .1 adjacent to thediaphragm. For purposes of clearness, the sound tube 2 is not shown inFig. 2.

The ring 5 is preferably removable and may be made of rubber oriother,suitable material. This ring is placed between the diaphragm 3 and theface of the body 1 to space the diaphragm the correct distance from theface of the body 1 and from the opening of the sound tube 2. The ring 5,however, may be formed integral with the body 1 and of a predeterminedthickness so as to definitely fix thedistance-between the face of thediaphragm 3 and the adjacent face of the body 1 or the opening in thesound tube 2. The clamping ring 4 may be recessed, as better shown bythe dotted line 8 in Fig. 8 to accommodate both the diaphragm and therub ber ring 5. The clamping ring 4 is slotted to form a passage for thestylus bar 13 when later to be described.

Screwed, or otherwise rigidly fastened to the body 1 is a supportingplate 9 to which the ends of a torsion spring 10 are secured.Intermediate the points of connection of the spring to the plate, theplate is recessed, as illustrated, the spring bridging the recess.

However, if desired, instead of using the plate 9 suitably spaced lugs11 may be cast or fastened on to the clamping ring 4 as H.- lustrated inFig. 8.

The torsion spring, the purposes of which will now be described, maycomprise a thin piece of metal. For example steel of 20/1000 of an inchthickness may be used.

Inthe present types of sound reproducers and recorders in which thestylus bar is usually actuated by a record, the stylus bar is usuallymounted on pivots and has no tendency to return to its normal positionafter it has been actuated. Therefore it will lag appreciably behind thevibrations impressed upon it and returnto its normal position only as aresult of its being moved by the record or the diaphragm. When thediaphragm is so hampered it will not produce a true tone or faithfulreproduction but a distorted wave. To eliminate this undesirable actionI actuate my stylus bar with a torsion spring.

The end portions only of the torsion spring engage the plate 9 or thelugs 11, these end portions being provided with screw holes forfastening the torsion spring onto the plate 9. The stylus bar is rigidlysecured to the spring, preferably .at the center thereof, and extends tothe center of the diaphragm. A

cured to the stylus bar. This lug may project laterally and be providedwitha bore v to receive a stylus and a thumb screw to retain the stylustherein. As on example, a torsion spring of less width than its end orsupporting portions may be used, the spring having a small centralenlargement so that the stylus bar or lug supporting the'same may beconveniently fastened thereto by screws. This type of spring isillustrated in Fig. 7.

A stylus bar so mounted can vibrate by twisting the narrow portions ofthe torsion spring. it or instance, in the case of reproduction of soundfrom lateral cut records thesound grooves of the record are lateral ofthe path ot movement and the record transmits a lateral movement throughthe stylus to the stylus bar by twisting the stylus bar about thelongitudinal torsional axis of the torsion spring. The width of thespring in the direction of motion of the stylus is sulfficiently greatto prevent any lateral movement of the spring itself at the point of thesupport of the stylus bar, so that the spring itselt allows only atorsional or twisting movement similar to the movement which the stylusbar would have if it were mounted on pivots. itt the same time, thestylus bar is returned to its normal position by the torsion spring nomatter in what direction it has been moved or twisted by the action ofthe record on the stylus. This return is rapid, the vibrating period orcycle of the stylus bar and spring assembly being in direct proportionto the breadth and thickness and inversely proportional to the length ofthe torsion spring. T make the torsion spring relatively short andthick, using for instance, steel 20/1000 of an inch in thickness. Such aspring has such a high natural 'frequency of vibration that it does nothave any tendency to blur or distort the sound waves transmitted throughthe stylus bar to the centerof the diaphragm. Further, it raises thepitch oil the stylus bar 13 and actuates it while lreeping the pitch ofthe stylus bar higher than that ot the human register. Therefore thestylus bar has no tendency to swing in uni son with, or to impress itsown period of vibration on the vibrations received from the record.

Another point at which sound waves are distorted in many talkingmachines is at the center of the diaphragm where there is a combinationof a slow moving diaphragm and a slow moving stylus bar which must beovercome by the power transmitted from the record. The torsion springdescribed is of sutlicient strength to actuate the diaphragm also. Thusthe hey note of the entireassemblage as well as each part is raisedabove the midi his range. This gives the stylus bar and the assemblage aperiod of vibration or key note which is out of the audible range ofvibration and consequently the combined diaphragm stylus bar and springsdo not synchronize with impressed vibrations and have no tendency toswing in unison with them or to impress their own period of vibration onthem. Ubviously, the same is true of the torsion spring itself.Therefore, vibrations which are carried up the stylus barto thediaphragm are substantially free from chatter, and any tendency of thestylus bar or the torsion spring to vibrate in unison with impressedvibrations and transfer the resultant vibrations to the diaphragm so asto blur the sound reproduction or recordation is eliminated, Suchvibrations as are impressed upon it to cause it to vibrate in unisontherewith will be only such sounds as will not affect the human ear, asthey will be above the audible range. Since the stylus bar and diaphragmthus are actuated and are raised in pitch by a torsion spring of such ahigh period that they Will not appreciably distort the impressedvibrations, T can employ a magnetically sensitive diaphragm, that is, adiaphragmwhich is composed of or includes soft metal and which diaphragmhas practically no period of vibration of its own.

in some cases, however, I prefer to use a diaphragm of spring temperedsteel or other spring tempered material, preferably in the form oi adisk mounted as a diaphragm in the diaphragm ring of the reproducer. Tnsuch cases, due to the fact that the diaphragm has a spring action andwill return to its nor-. mal position almost as rapidlv as it is movedby the vibrations of the stylus bar, the stylus bar may be mounted onpivots in the usual fashion and without a torsion spring.

For instance, the spring tempered diaphragm in Fig. 13 has its owntendency to re turn to normal position and to return the stylus bar andhold the stylus bar at a higher pitch than the ordinary diaphragm would.do and consequently, the stylus bar may be mounted onpivots, as stated.

As set forth in the objects of my invention, it is necessary to have adiaphragm so deli cately poised that it will respond to very slightvariations in tone or magnitude of vibration and at the same time ofsuch resiliency that it is capable of swinging through a greateramplitude than the greatest arhplitude of vibration that will beimpressed upon it when in use. "When ll speak of a resilient diaphragm,I mean one which will reach the limit of its greatest vibrationsubstantially in unison with the impressed vibration and which willreturn-to its normal position as rapidly as the cycle of the particulartone which is being impressed. In other Words, the diaphragm must notlag appreciably behind the impressedvibrations or there will be What isknown as distortion. This distortion, in reality resultants of thediaphragm tone caused by its lagging behind the impressed vibration, isovercome by the torsion spring, as described, and my magneto electriccircuit, later tobe described and a diaphragm having no key note as aWhole, but having a period of vibration below the audible range.

l have found that many diaphragms of a single substance have a fixedperiod of VlbI'il-mtion or a key note to which they will respond morereadily than they will to any other period of vibration. Further, l havefound that a velvety softness can be imparted to the lld blotting paper,may be used. In the case of reproduction of the human voice, forexample, such a soft fibrous working surface on a diaphragm will give tothe sound waves leaving the diaphragm a more natural human tone. Also itwill give an improved tone to the sound wave of whatever instrument isbeing reproduced.

Further, I have found that if a diaphragm is divided into two or morediaphragms or portions by the use of a smaller diaphragm or by ringsformed or riveted, or otherwise secured in place on the diaphragm, eachof the portions will have a period of vibration of its own and thediaphragm will be in effect, a

compound diaphragm having no key note as a whole.

I shall now discuss a numberof diaphragms embodying the principles aboveenumerated.

The diaphragm illustrated in Figs. 9 and 10 has been divided into two ormore diaphragms or areas by use of a ring or annulus 1 f secured inplace on the diaphragm by rivets 15or otherwise. This ring, or rings, ifmore than one is used, may be of the-same material as the diaphragm orof a stiffer material. A diaphragm with rings so mounted will have morethan one period of vibration. From observation, it appears that theouter diaphragm or portion 16 will have a low period of vibration, thering section or annulus 14 will have a higher period of vibration andthe inner diaphragm or central circular portion 17 will have a stillhigher period of vibration. Each area responds to different periods ofvibration and each area will respond more readily to its own key note.For this reason the diaphragm as illustrated has.

no key note to which it will respond as a whole.

I have found that a diaphragm divided into three diaphragms or portionsas' illustrated in Fig. 9 gives very desirable results in the separationof sounds of different frequencies-of vibration. mingling vibrationsresulting from the voice waves of a quartet traveling up the stylus barto the center of such a diaphragm appear to be separated and each voicebrought out clear and distinct and separate from the other voices, theouter diaphragm being responsive struments or of a plurality of soundshave As a concrete example the co-.

ing different wave lengths is obtained. By the use of such a diaphragm,I have been able to distinguish two voices singing in harmony.

To use this type of diaphragm effectively in my magneto electricreproducer it is only necessary that the ring 14 be magneticallysensitive. The material which I use for the diaphragm in such casemay'either be magnetic or non-magnetic, in fact, any material commonlyused for diaphragms is.satisfactory.

These rings will be operated on by the magneto and electric members ofmy reproducer and will give substantially the same results as though Ihad used a completely magnetic or magnetically sensitive diaphragm.

' This type of diaphragm may be covered on one side by a soft fibrousmaterialas above mentioned. This fibrous surface imparts to the toneproduced by the'diaphragm, especially in the case of reproduction of thehuman voice a more natural tone which I have not 1 been able to producewith a diaphragm having a smooth-,or. glazed working surface.

Fig. 10 is a cross-sectional view of this diaphragm with rings rivetedin place on opposite sides. These rings divide the diaphragm into threediaphragms or portions for the purposes enumerated above; The diaphragmitself may be made of any substance commonly used for diaphragm or maybeeither magneticor non-magnetic, as stated.

In Fig. 11 is illustrated a diaphragm, composed of two or moresubstances. For instance, the diaphragm may be composed of a materialeither magnetic or non-magnetic and a soft fibrous material 18 or of ahard fibrous material with a soft fibrous material or of mica and a softfibrous material, the object being to secure a resilient diaphragm witha soft and roughened fibrous surface which produces clearer tones thanthe harsher or metallic side of the diaphragm.

'Fig. 12 illustrates a diaphragm. divided into three diaphragms orportions, each having its own key note and in addition has the advantageof a diaphragm composed of two or more substances'as illustrated in Fig.11. [As stated, the outer portion appears to vibrate more in unison withthe lower tones, the

"superimposed rings 19 in unison with tones of the middle register andthe small inner portion responding more'readily to tones of the upperregister, for example, the soprano.

The soft fibrous covering produces better and more natural tones in allregisters and thus renders the diaphragm especially effective forreproducing the human voice clearly. In such a diaphragm the desired anddistinct separation of the voice tones of differentpitches is obtainedand slurring and blurring are eliminated, or are so-reduced, as to beunnoticeable. This soft fibrous surface is designated at 20.

ment operatively associated With the dia-' phragm for eflectingactuations of the same, and means including a member operativclyvassociated With said diaphragm and said element tor impressing on saiddiaphragm and element a period olt' vibration above the audible range.

4.. in a sound apparatus a magnetically re-- sponsive element, means toproducea magnetic flux at each side of the'center of the path atvibration o'l said element transverse to the path of movement of saidelement and spaced from the normal position of rest of said element saidflux yieldably opposing vibrations of said elementnear its outer lim itsof movement, the ell'ect of said magnetic torce diminishing as theelement comes near to its normal position of rest.

5. A. sound translating apparatus including a vibratable element andmeans producing a magnetic lllDI in which said element moves duringvibration for opposing movement of said element, said means includingmagnet poles positioned on longitudinally opposite sides of the centerof the path ot vibration or said element. and individually shortcircuited coils arranged on said poles.

6., A sound translating apparatus includ ing a vibratable magneticallysensitive elcment, a magnet producing a tlux across and atlongitudinally opposite sides of the center ot the path of vibration ofsaid element, and coils in inductive relation to said magnet, said coilsbeing unconnected in any extranenus translating circuit.

7. ln a sound translating device, a vibratalole element, said elementbeing responsive to magnetic tins, and means to vibrate said element,magnets opposing movement of said element in each direction or vibrationfrom its normal position of rest, said magnets being arranged at leastone at each of 'the lontill gitudinally opposite sides of the center ofthe.

ing movement of said element from its normal position of restsubstantially equally in each direction of vibration.

9. A sound reproducing device including a sound diaphragm, saiddiaphragm being sensitive to magnetic flux andmeans to vibrate saiddiaphragm, opposed magnets arranged at opposite faces of said diaphragmand producing flux across the path of movement thereof for opposingmoving of said diaphragm in each direction of its vibration. 10. A soundreproducing device including vibratable sounding diaphragm, means tovibrate said diaphragm, a magnetically sensitive element connected tothe diaphragm and vibratable therewith, magnets spaced apart and onlongitudinally opposite sides of the center of the path of vibration ofsaid element andproducing flux across the path of vibration thereof,said flux opposing movement of said element and diaphragm in eachdirection of vibration.

11. A sound reproducing apparatus including a sound producing diaphragmadapted to be vibrated, means to vibrate said diaphragm, a vibratableelement responsive to magnetic flux connected to said diaphragm,magnetic means for producing magnetic flux across the path of vibrationof said element at longitudinally opposite sides of the center oit saidpath, said flux yieldably opposing movement of said element anddiaphragm sub stantially equally in each direction or vibi" tion fromtheir normal position of rest.

12. ln a sound translating device, a vibratable element includingconducting ma terial whereby said element is responsive to magneticflux, and means to vibrate said element, magnets for producing amagnetic flux across the path of vibration of said element atlongitudinally opposite sides of the center of said path of vibration,said flux yieldably opposing movement of said element from its normalposition of rest in either direction of movement from said position oi.rest.

13. A sound reproducing device, including a vibratable soundingdiaphragm, said diaphragm being responsive to magnetic ilux, means forvibrating said diaphragm, and means including magnets for producing a\magnetic flux for yieldably opposing movement of said diaphragmsubstantially equally in each direction of vibration from its normalposition of rest.

1%. A sound translating device, including a vibratable member,saidmember being responsive to magnetic flux, and magnetic meansarranged for producing a magnetic flux across the path of vibration ofsaid memher at longitudinally opposite sides of said path for opposingvibration of said member equally in each direction of vibration from itsnormal position of rest, and means comprising coils inductive relativewith said magnets for varying the opposing effect of said flux,

Ill.

Wop

- said coils being unconnected in any extraneous rest, a stationary coilin inductive relation to said flux for efiecting variations in saidflux, said coil being unconnected in any extraneous translating circuit.

16. A sound translating device, including a vibratable element, saidelement being responsive to magnetic flux, magnets arranged forproducing magnetic flux across the path of vibration of said element atlongitudinally opposite sides of the center of said path, said fluxyieldably opposing movement of said element in either direction ofvibration, coils inductively associated with said magnets for changingthe intensity of said flux, said coils being unconnected in anyextraneous translating circuit.

17. A sound translating apparatus, including a vibratable element andmeans to vibrate said element, said element being responsive to magneticflux, meansincluding magnets arranged at longitudinally o posite sidesof the center of the path of vi ration for produc'in flux across saidpath for yieldably opposing movement of said element from its normalposition of rest, and coils in inductive relation with said magnets,said coils being unconnected in any extraneous translating circuit. a

18. A sound translating device, including magnetically responsivevibratable element, a plurality of magnets arranged to cause magneticflux across the path of vibration of said element at longitudinallyopposite sides of the center of said path, part of said magnets beingarranged at one of said longitudinally opposite sides of said pathcenter and part'at the opposite side, coils on said magnets, said coilsbeing unconnected in any extraneous translating circuit. r 19. A soundtranslating device, including a vibratable member responsive to magneticflux, means comprising a plurality otvmagnets for producing a field inwhich said memher is adapted to move during vibration, coils on saidmagnets, said coils being connected with each other.

20. A sound translating device, including a vibratable memberresponsiveto magnetic flux, sets of magnets positioned at longitudinally oppositesides of the center of the path of vibration of said member, coils ininductive relation to said magnets, the coils of one side and formingtherewith a closed local circuit;

22. In a sound translating device, a vibratable member responsive tomagnetic flux, opposed magnets positioned at longitudinally oppositesides of the center of the path of vibration of said member, the fluxesof, said magnets opposing each other, coils in inductive relation tosaid magnets, said coils being unconnected in any extraneous translatingcircuit.

23. In a sound translating device, a vibratable member responsive tomagnetic flux, opposed magnets positioned at longitudinally oppositesides of the center of the path of vibration of said member, coils ininductive relation to said magnets, the coils of the magnets at one ofsaid sides of said center of the path of vibration being connected in aclosed local circuit with the coils of the magnets at the opposite side.

24. In a sound translating device, a magnetically sensitive vibratableelement, magnets arranged to produce magnetic flux across the path ofvibration of said element at longitudinally opposite sides of the centerof the said path of vibration thereof, coils in inductive relation tosaid magnets, said coils being connected together in a. closed localcircuit.

25. A sound recording device, including a vibratable element, saidelement being magnetically responsive, a translating element, saidtranslating element being vibratable consequent upon vibrations of thefirst mentioned element, and means to vibrate said first mentionedelement, means including magnets arranged for opposing magnetically themovement of one of said first mentioned elements substantially equallyin each direction of vibration from its normal position of rest.

26. In a sound translating device, a diaphragm, a translating elementvibratable consequent upon vibrations of said diaphragm, magnetic meansyieldably opposing movement of said elements substantially equally ineach direction of vibration from their normal position of rest.

27. In a sound translatingdevice, a magnet, a diaphragm, a conductorcarried by an.

annular portion of said diaphragm and disposed in the field of saidmagnet, and means for energizing said conductor whereby actuations ofsaid diaphragm are effected.

28. In a sound translating device, a magnet, a diaphragm, anannularconductor element carried by an annular portion of the lid lid

diaphragm and concentric therewith, said conductor element beingarranged for vibration in the field of said magnet, a coil on saidmagnet, and means to energize said coil whereby vibrations of saidconductor and annular portion of said diaphragm are elfected.

29. In a sound translating device, a diaphragm, an element of conductingmaterial carried by an annular portion of said diaphragm and concentricwith said diaphragm, magnetic means for producing aflux in which saidelement is adapted to move during vibration, means to vary said elementand flux to efiect actuations of said diaphragm.

30. in a sound translating device, a vibratable diaphragm, a magnetproducing a magnetic flux, a magnetically responsive element carried byan annular portion of said diaphragm and arranged to vibrate therewithand in said flux, said flux opposing movement I of said diaphragmthrough the medium of said annular portion of said diaphragm when thediaphragm is vibrated and means to vibrate said diaphragm.

31. In a sound translating device, a vibratable diaphragm and an elementincludin conducting material and forming a part 0 the face of thediaphragm, means comprising a magnet arranged to produce a flux in"which said element is adapted to move duringvibration, and means tovary the intensity of said fiun. v

32. A sound translating device including a magnetically sensitivevibratable element,

means "for vibrating said element, and means includin opposed magnetsarranged at longitudinaTly opposite sides of the center of the path ofvibration of said element, and producing flux across said path foryieldabl opposing vibration of said element in eac direction citvibration from its normal position cit rest.

33. A sound reproducing device comprising a magnetically sensitivesounding diaphragm, means to vibrate said diaphragm, and means includingmagnets arranged at opposite faces of said diaphragm for yielda lyopposing movement of said diaphragm in each direction of vibration fromits normal position of rest.

In testimony whereof, I hereunto aflix my signature.

WALTER RICHMOND.

CERTIFICATE or CORRECTION. 7 Patent No. 1,845,988. I Granted February16, 1932, to

WALTER RICHMOND.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2;line 123, for the word "on" read one; page 3, line 14, strike out"itself"; page 4, line 97, for "diaphragm" read diaphragms, and line113, for "advantage" read advantages; page 6, line 123, claim, 1, for"or" read of, and line 127, claim 2, for "translated" read translating;page 7, line 98, claim 11, for "or" read of; page 8, line 40, claim 18,before "magnetically" insert the article a, and line 56, claim 19, after"other" insert the words in a closed local circuit; page 9, lines 15 and16, claim 29, strike out the words "element and" and insert the sameafter the word "said" in line 16, of same claim; and that the saidLetters Patent should be read with these corrections therein that thesame may conform to the record of the case in the Patent Office.

Signed and sealed this 22nd day of March, A. D. 1932.

v M. Moore, (Seal) Acting Commissioner of Patents.

